The role of host cell proteases in SARS-CoV infection is not limited to cleavage of the spike protein; in fact, spike binding to ACE2 activates the disintegrin and metallopeptidase domain 17/tumor necrosis factor-converting enzyme (ADAM17/TACE) and its close relative ADAM10 [7], which cleave the ectodomain of ACE2, resulting in shedding of ACE2 [8]. Here, ACE2 is linked to severe acute respiratory syndrome.